1. Field of the Invention
This invention relates generally to television receivers, and more particularly to horizontal deflection circuit arrangements of television receivers including a horizontal deflection coil for scanning an electron beam in a cathode ray tube.
2. Description of the Prior Art
In the reproduction of a television signal, particularly, such a television signal as once recorded and then reproduced by a video tape recording and/or reproducing apparatus, a television receiver is often supplied with a television signal containing a horizontal synchronizing signal fluctuating in its frequency in the cause of, for example, deviation of the tape speed of the video tape recording and/or reproducing apparatus.
Generally, a horizontal deflection circuit of a television receiver is provided with an AFC (Automatic Frequency Control) circuit which controls a horizontal oscillator with an output of a phase comparator comparing the phase of the output of the horizontal oscillator to the phase of the horizontal synchronizing signal of the received television signal to carry the output of the horizontal oscillator in synchronism with the horizontal synchronizing signal.
Accordingly, when the frequency of the horizontal synchronizing signal of the received television signal fluctuates from a predetermined correct frequency (15.75KHz), the frequency of the output of the horizontal oscillator fluctuates, and therefore the frequency of a drive signal for a horizontal output switching device by which a horizontal deflection current is supplied to the deflection coil, also fluctuates.
In conventional television receivers, even if such fluctuations occur, it is possible to get a reproduced picture. However when the frequency of the drive signal fluctuates, the horizontal size of the raster is undesirably varied, that is, if the frequency of the drive signal decreases, the horizontal deflection current increases and accordingly the horizontal size of the raster becomes larger and on the contrary if the frequency of the drive signal increases, the horizontal deflection current decreases and accordingly the horizontal size of the raster becomes smaller.